1. Field of The Invention
This invention generally relates to a hypodermic syringe and needle assembly of the type capable of encapsulating the exposed needle for the safety of health care personnel and patients.
2. Description of Related Art
Because of the potential danger to medical and health care workers and others caused by contact with or puncture from a used hypodermic needle, many proposals have been suggested to reduce or eliminate this danger.
Previously, some disposable hypodermic syringes have been manufactured with a protective detachable cover over the needle which can be too easily removed or lost, for example, should the syringe be dropped or knocked against some object.
Protective sleeves for hypodermic needles have been previously suggested in U.S. Pat. Nos. 3,040,743 to Naess; 3,314,428 to Johnson et al.; 4,695,274 to Fox; 4,655,751 to Harbaugh and 4,772,272 to McFarland.
The above prior art syringes include a protective sleeve which is fitted over the needle. The protective sleeve is slid away from the needle to accomplish the injection. The syringes are intended to be disposable, that is, intended for one-time use only.
More recent related syringe disclosures have been disclosed in U.S. Pat. Nos. 5,125,898 to Kaufhold, Jr. et al.; 5,211,629 to Pressly, et al.; 5,211,628 to Marshall; 5,069,225 to Okamura; 4,974,063 to Jacobs; and 4,904,242 to Kulli. Except for Okamura and Jacobs, the remaining four patents use passive means, that is, coil spring energy or differential pressure, to expel the needle from the syringe into a tubular depository inserted within the syringe. Okamura and Jacobs provide for release of the needle without providing for direct capture of the needle.
Kaufhold, Jr. et al., U.S. Pat. No. 5,125,898, discloses a disposable hypodermic syringe for injecting fluid into a patient. Axial force is applied to an air evacuated plunger tube, which acts as a needle storage container, that ruptures two sacrificial components, one which releases the needle from the syringe body, and the other that separates a pressure seal member at the bottom of the plunger tube. When these actions are performed, the pressure seal component attaches to the needle assembly and is pushed into the plunger tube by ambient air pressure.
As in Kaufhold, Pressly, et al., U.S. Pat. No. 5,211,629, describes a hypodermic syringe for injecting fluid which, with applied force by a containment tube, ruptures sacrificial components to free the needle and also to pierce an opening through the closed end of the plunger tube for needle passage and containment. The energy to expel the needle into the containment tube is supplied by a previously installed and charged coil spring.
Marshall, U.S. Pat. No. 5,211,628, also incorporates a coil spring to provide the energy to withdraw a needle into containment within a closed tube which acts also as the plunger to inject fluid. The spring is maintained compressed between the closed top end of the tube and another tapered component press fitted into the lower end. When axial force is applied, the tube lower end deflects outward a needle holding collar to free the needle. At a predetermined axial motion, the tapered fit holding the spring force is released allowing the spring to push the needle into containment.
Kulli, U.S. Pat. No. 4,904,242, describes a needle removal, spring expelling and containment design similar in action to Marshall. In addition, except for the sacrificial components used by Pressly, et al. it appears that the three disclosures are similar, providing like actions and require coil spring energy to expel the needle. In addition, these designs all require high axial forces to rupture and/or release the hold on the needle. This high applied force contributes to the safety hazard to the operator and patients or others nearby. Kulli's needle is cantilevered from the syringe holder joint and operates as a hinged joint, that is, the needle injection point actually pivots from the tip of the holder because of the clearance required between the needle ferrule groove and the holder leaves of the syringe body to accomplish needle installation and separation to/from the syringe body. Being a hinged joint, the resulting pivoting action of the needle during the penetration in the skin can result in skewed needle penetration in the skin and beyond and possibly cause injury to the patient. On the other hand, tightening up the clearance at the joint will only increase the axial force required to expel the needle and aggravate the already dangerous hazard to the user or others.
Accordingly, there is a need for an improved, simple and inexpensive needle-bearing syringe which can be operated without using high axial forces, can expel the needle simply and directly, not passively, can be safely handled after use and whose operation can be easily learned. The previously described patents require several actions, from several components, to accomplish needle removal. The various inter-related mechanical operations compound the possibility that mechanism malfunctioning will occur especially when components are plastically deformed. Similarly, the use of passive energy devices (i.e. springs, etc.) where no operator control can be exercised if needed, reduces confidence in the successful operation of the mechanism. This is complicated by the effects on clearance that the passive device must operate within to compensate for the resulting plastic component distortions and/or ruptures incorporated in the designs.